Electric furnace.



UNITED STATES PATENT OFFICE.

WILLIAM C. ARSEM, OF SCHENECTADY, YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC FURNACE.

naces, of which the following is a specification.

My present lnvention comprises an electric furnace having a heating chamber and a condensing chamber, and having various elements so constructed and arranged that metals or compounds may be vaporized in the hot zone and then condensed in the cooler zone. According to my present invention, the whole operation of vaporizing and con densing can be carried out in a vacuum or in a suitable gas or gases.

My improved furnace embodies many novel features and can be used to advantage for the fractional distillation of metals, ele ments and compounds and as a means for carrying out various other metallurgical processes.

In the accompanying drawing Figure 1 is a sectional elevation of a furnace with the crucible removed from the heating chamber so that the heating elements may be clearly seen; Fig. 2 is a sectional plan of the same; and Fig. 3 is an end elevatio with certain parts cut away.

The main envelop of the furnace consists of a rectangular boX 1, preferably of gun metal with a coating of tin, provided with a cover 2 bolted securely in place. The cover 2 has man-holes 3 and 4 located respectively, above the cold and the hot zones of the furnace. Lead gaskets 5 can be used under the covers to make air-tight joints. The heating element of the furnace consists of four graphite grids 6, 7, 8 and 9 sawed transversely and with their corners rounded off, as shown in the drawing, so that when current is passed through them they will attain a uniform incandescence throughout substantially their entire length. Current is supplied to these graphite resistance elements by way of water cooled copper tubes 10 and 11 passing through insulating bushings in the end of envelop 1. The tubes are clamped, respectively, in copper blocks 12 and 13, which in turn are bolted to the graphite grids 6 and 9. The other ends of these grids make contact respectively with the graphlte blocks 14 and Specification of Letters Patent.

Application filed August 18, 1909.

Patented Nov. 21, 1911.

Serial No. 513,407.

15 and these make electrical connection with the lower pair of grids. A cross connection 16 of graphite at the extreme end of the furnace completes the electrical circuit. For the sake of avoiding confusion on the drawing, the current supply cables for the tubes 10 and 11 have been omitted but the rubber hose for conducting water to these terminals for cooling purposes is shown at 17 and 18. The water used for cooling may be conveniently discharged into the space surrounding the furnace, as indi cated in Fig. 1 by the end of tube 10 eX- tending into the water.

The above described heating element, consisting of the four grids 6, 7, 8 and.9, is inclosed in a rectangular heat insulating screen, the graphite walls of which are made double throughout with an intervening packing of graphite powder. The bottom member .19 of the screen rests on insulating buttons 20 of lava and supports the end walls 21 and 22 and also the side walls 23 and 24. The top member 25 rests on the tops of the four side walls. This heat insulating screen serves to limit the radiation of heat outward and serves to reflect and concentrate the heat on the rectangular space inclosed by the heater grids. Within this space may be introduced a rectangular c'rucible 26 of graphite or fire clay carrying the charge to be treated. The crucible may conveniently be supported on a rectangular platform 27 carried on graphite standards 28 which pass down tl'irough holes in the heat insulating screen and terminate in insulating bushings 29. The crucible is preferably provided with a cover to prevent free escape of vaporized material except through the tubular outlet 30 which leads to the condensing chamber 31 at the other end of the furnace.

The condensing chambermay advantageously consist of an earthenware pot fitting snugly against the water-cooled walls of the envelop 1 and of suiiicient size to insure complete condensation of all elements distilling over from the hot zone of the furnace.

The condensing chamber may be provided with a cover 32 preferably having an outlet 33 for the ready removal of air when the entire furnace is pumped out by way of pipe 34 leading to a vacuum pump. When the furnace is running as a vacuum furnace the continuous operation of the vacuum pump is ordinarily desirable. Inert or other gas may be admitted to the furnace through suitable extensions of the exhaust pipe 34. The main envelop 1 of the furnace is maintained cool by water circulating below and on all sides of it up to a level just below the man-hole covers 3 and 4:. These are preferably left unsubmerged for the more ready introduction and removal of material.

The apparatus above described may be used for a great variety of purposes and I have found it very serviceable for the treatment of ores and for the fractional distillation of metals. A process for the carrying out of which my form of furnace is suitable is described and claimed in my Patent No. 984,503 filed August 18, 1909. In accordance therewith calcium carbid is decomposed at a high temperature, and the metallic calcium is volatilized and carried over to the chamber 31 where it is condensed.

It will be understood that the operating temperature of the furnace is governed somewhat. by the nature of the process in which it is being used and that the degree of vacuum and the presence or absence of an inert or active gas is also governed by the demands of the process in hand.

Alternating current can with advantage be used in the heater grids and any temperature up to the vaporizing point of carbon can be obtained and constantly maintained for any length of time at a pressure of a fraction of a millimeter of mercury. The material under treatment does not come in contact with the heating elements and, since no chemical action occurs between the two, many operations can be carried on which would be impossible in the more usual types of electric furnaces wherein contact of the heated substance with the heating element is unavoidable.

In charging and discharging the furnace it is only necessary to remove the man-hole covers 3 and 4, whereupon, after removal of the upper screen 25, the crucible 26 can be filled with a new charge and the condensing chamber 31 relieved of the condensed material or even lifted out bodily and replaced by another similar earthen pot.

What; I claim as new and desire to secure by Letters Patent of the United States is- 1. In an electric furnace, an air-tight envelop, means for maintaining a cooling fluid about said envelop, a closed crucible within said envelop, means for heating said crucible, and a condensing chamber communicating with said crucible and in heat-conveying relation to said fluid.

2. In an electric furnace, an air-tight envelop, a heating chamber within said envelop, a closed crucible situated in said chamber, a closed receptacle within said envelop for receiving vaporized material and means for conducting vapors from the crucible to said receptacle.

3. The combination of an air-tight envelop, a resistance heater within said envelop, means for supporting a charge in proximity to said heater and out of contacttherewith, a condensing chamber, and means for conducting vaporized material from said crucible to said condensing chamher.

4. The combination of an air-tight envelop, graphite heater grids within said envelop, a heat insulating screen inclosing said grids, a platform for supporting a crucible between said grids, and means for conducting vapors from said crucible to the cooler region outside said screen.

5. In avacuum furnace, a heater comprising a plurality of graphite grids electrically connected and inclosing a zone to be heated, and a heat insulating screen surrounding said grids, said screen being in part removable to give access to the heat zone.

6. In a vacuum furnace, the combination of a metal envelop, a graphite heater within said envelop and consisting of grids insulated from the walls of said envelop, a platform for holding a crucible inthe rectangular space inclosed by said grids, and a heat reflecting shield surrounding said heater and having a cover removable to give access to said crucible.

-7. In a vacuum furnace, the combination of a metal envelop, water-cooled terminals passing through said envelop and insulated therefrom, a heater connected with said terminals and consisting of a plurality of grids connected in series and forming a rectangular space for the reception of a crucible to be heated, and a heat reflecting screen consisting of graphite boxes packed with refractory powder and inclosing said grids to concentrate the heating effect on the crucible and its charge.

8. The combination of a water-cooled metal envelop, means for maintaining a vacuum therein, a resistance heater within said envelop, a crucible inclosed by said heater, a heat reflecting screen inclosing said heater, and a refractory receptacle in contact with the cold walls of said envelop and having an inlet communicating with said crucible.

In witness whereof, I have hereunto set 'my hand this 17th day of August 1909.

WILLIAM C. ARSEM. Witnesses:

BENJAMIN B. HULL, MARGARET E. WOOLLEY. 

